Nb3Sn superconducting wires with artificial pinning centers

The Nb3Sn wires will be fabricated based on the “Artificial Pinning Center” (APC) technique.

The details of the specifications of the wires are listed below:

1. The wires use an Nb alloy tube with the composition of Nb-7.5wt.%Ta-2wt.%Hf or Nb-7.5wt.%Ta-1wt.%Zr, with the deviation of the Ta percentage no more than 1 wt.% and the deviation of the Hf or Zr percentage no more than 0.3 wt.%. The Nb-7.5wt.%Ta-2wt.%Hf or Nb-7.5wt.%Ta-1wt.%Zr tubes must be properly annealed, with initial hardness below 100 HV.
2. The wires must have proper percentages of Sn, Cu, SnO2 in the powders, so that the filaments are fully reacted.
3. The wires have a 61-filament or 217-filament array, with the Cu/non-Cu ratio no more than 1.5.
4. The wires are drawn to diameters of 0.5-1.0 mm, with filament size smaller than 70 micron.

All the final wires are to be delivered to Fermilab.